Which of the following statements is not correct?

Options

A. Copper liberates hydrogen from acids
B. In its higher oxidation states, manganese forms stable compounds with oxygen and fluorine.
C. `Mn^(3+)` and `Co^(3+)` are oxidising agents in aqueous solution.
D. ` Ti^(2+)` and `Cr^(2+)` are reducing agents in aqueous solution.

Explanation

To determine which statement is not correct regarding the D and F-block elements, we need to analyze the provided information and identify the statements related to the properties and reactions of these elements.

### Step-by-step Solution:

1. **Understand the Context**: The question revolves around identifying incorrect statements about D and F-block elements, particularly focusing on their reactions and properties.

2. **Review the Reaction**: The transcript discusses the preparation of potassium permanganate (KMnO4) from pyrolusite (MnO2) using potassium hydroxide (KOH) and an oxidizing agent. The reaction can be summarized as:
- **Reaction 1**: 2MnO2 + 4KOH + O2 → 2K2MnO4 + 2H2O
- **Reaction 2**: 2K2MnO4 + 4HCl → 2KMnO4 + MnO2 + 2H2O + 4KCl

3. **Identify the Oxidizing Agents**: The transcript mentions two oxidizing agents that can replace air in the above reactions:
- Potassium nitrate (KNO3)
- Potassium chromate (K2CrO4)

4. **Evaluate Statements**: Now, we need to evaluate the statements provided in the question. Since the question does not provide specific statements, we will assume common misconceptions or statements about D and F-block elements that could be incorrect.

5. **Common Misconceptions**:
- D-block elements are not transition metals.
- F-block elements are not involved in any oxidation-reduction reactions.
- All D-block elements have a +2 oxidation state as their most stable state.

6. **Identify the Incorrect Statement**: Among the common misconceptions, the statement that "F-block elements are not involved in any oxidation-reduction reactions" is incorrect. F-block elements, particularly the lanthanides and actinides, can participate in redox reactions.

### Conclusion:
The statement that is not correct regarding D and F-block elements is that "F-block elements are not involved in any oxidation-reduction reactions."